Modern Magic or Occult best ideas

[RenleyRenfield]

So there are a number of new and old games which in some way address modern real world with magic and or the occult (summoning, angels, demons, rituals etc etc)

What single mechanic or game feature is your favorite from any such game?

That is to say, whether you liked the game over all or not = what was some aspect that specifically pertained to modern magic or occult roleplay that was really fun for you?

 

[Theory of Games]

Being able to create your own spells is IME always the META. GURPS allows this.

As far as rpg magic in modern times, I find how using magic in Call of Cthulhu/Delta Green can drive your PC insane very entertaining.